Completion operations, for both main and lateral wellbores, may include gravel packing, fracturing, acidizing, cementing, and perforating, for example, as well as running and hanging a completion string within the wellbore. Completion strings may include various completion equipment such as perforators, filter assemblies, flow control valves, downhole gauges, hangers, packers, crossover assemblies, completion tools, and the like.
Acidizing involves stimulation by acid under matrix conditions in carbonate formations to create highly conductive flow channels. Such channels may be known as wormholes. Wormholes may be formed when the matrix of the porous and permeable rock is dissolved by corrosive fluids, such as hydrochloric acid. These flow channels promote fluid communication between the wellbore and hydrocarbon-bearing formation, thereby allowing hydrocarbons to flow into the wellbore at a minimum drawdown pressure. Matrix acid treatment should be performed in such a way to form deep penetrating wormholes.
As such, one important treatment parameter that should be considered is injection flow rate. If the injection flow rate is too low, only permeable rock in the vicinity of the wellbore may dissolved. Therefore, matrix acidizing at higher rates may be preferred, as it may lead to better fluid coverage in the reservoir layers and more efficient wormhole production.
However, injection rates may be limited by treatment pressure constraints. Bottom hole treatment pressure should not exceed the fracture pressure for the formation, because fracturing during matrix acidizing may cause an unfavorable fluid distribution. In order to estimate the formation fracture pressure, a step up rate test may first be conducted.